A10C engine model

[Raistlen007]

Why not just start the mission without stores so you wont have to drop them and the pylons..?

 

I just wanted a quick baseline check to see if my tests were even in the ballpark. Since they're not I'm gonna assume for now my testing is wrong and I'm hoping someone can help establish a proper scenario for baseline, which takes not only the pylons into account but also temperature and pressure.

[Enduro14]

Well I'm not really a civilized person on certain matters. But this thread and the other that was closed is quite interesting. Didn't recently ED add a humidity factor to the game engine? Also if information is eventually provided or testing in all weather and weight drag config does prove our beautiful hog is not up to snuff can changes be made?

Do realize and I'm not here to defend fellow service members but some fellas around here have the true data and see it in person everyday. That being said I fully understand certain things due to contract may prevent certain accuracies.

Either way we should have a good discussion on this and take feedback not as criticism but as us as a community helping you maintain the highest levels of Allowed accuracy.

Also I have seen 3rd party developers base their FM on all the geek numbers and more importantly actual pilot feedback. Food for thought but I'm sure I just stated the obvious. Hog is one of my favs and in a couple weeks will get to see her up close and personal so hope the best for her in the sim as well.

[Vitormouraa]

Humidity factor for the Vortex IIRC. Vortex now is also based on humidity, and not only on load factor etc..

[Aginor]

I'm not really a civilized person

Sure, I ... wait, what?

 

Anyway, you have to realize that ED has certain advantages (and restrictions) that 3rd parties don't have. They also had pilots and documentation (some of it classified so they can't even tell us) available for building that PFM. So I fully understand they want A LOT of proof that something they did in cooperation with the real USAF is wrong and are hesitant to change it. Their source material used back then was of a very high "confidence level".

 

But I agree: We are so convinced *something* is wrong, we are up to the challenge of finding it, and I am happy that ED allows us to further research and discuss this and at least listen to us and validate what we find themselves.

That's a good thing, even if they don't change anything, because honestly: Even if it is wrong the difference might be considered small enough by most people to not justify a change of the PFM with all the work it causes.

[Enduro14]

Sure, I ... wait, what?

 

Anyway, you have to realize that ED has certain advantages (and restrictions) that 3rd parties don't have. They also had pilots and documentation (some of it classified so they can't even tell us) available for building that PFM. So I fully understand they want A LOT of proof that something they did in cooperation with the real USAF is wrong and are hesitant to change it. Their source material used back then was of a very high "confidence level".

 

But I agree: We are so convinced *something* is wrong, we are up to the challenge of finding it, and I am happy that ED allows us to further research and discuss this and at least listen to us and validate what we find themselves.

That's a good thing, even if they don't change anything, because honestly: Even if it is wrong the difference might be considered small enough by most people to not justify a change of the PFM with all the work it causes.

 

 

 

True that and what i was trying to get at with first line was i usually speak from emotion before the brain kicks in sort of thing... Bad Army Habbit

[SCU]

Maximal AoA, lift are exactly as they specified in the very specific official book... even the conversion from true AoA to the units at the gauge is authentic.

 

Very often pilots look at their muscle memory regarding the performance at not to the flight parameters... it's sad, but it is a very well known fact.

 

No one doubts this fact. What the pilot said in the reddit post (and what I have been trying to say for quite a while too) is that stall behaviour is much more forgiving in real life than in the sim. The stall parameters charts in the official documents states that after exceeding maximum AoA (of 25 units iirc) the plane starts to buffet. Nowhere does it state that wing dips and deep wing stalls occur like it does in the sim. Also all the A-10 videos available on youtube including cockpit recordings (HUD recordings & GoPro cams) show that the real life counterpart truly enough is a lot more forgiving when above critical AoA than the sim. I can provide you these videos & the stall charts if you want.

 

Something else regarding stalling, is the stall warning tone at high speeds. In the sim when above mach 0.7 and increasing the AoA the plane buffets and wing-stalls long before the stall tones (yes both of them). There is a HUD video of such a run on youtube where the pilot pulls the plane with the appropriate stall tones and even more AoA (visible by comparing the gun cross with the Flight Path Marker) than you can at the same speeds in DCS according to my testing, which I'm not saying are perfect but I tried this both in 1.5.x & 2.0x and I can't do the same AoA's as in the real life video without spiraling. This is detrimental to vertical high angle strafe runs (below -60° angle) where you have to pull the plane up at high speeds before hitting the ground in the sim. Just tell me if you want said video and I will share it.

 

 

Don't take this as criticism, I'm just really trying to help make this a better and more accurate plane for everyone :).

Edited August 4, 2016 by SCU

[Yo-Yo]

No one doubts this fact. What the pilot said in the reddit post (and what I have been trying to say for quite a while too) is that stall behaviour is much more forgiving in real life than in the sim. The stall parameters charts in the official documents states that after exceeding maximum AoA (of 25 units iirc) the plane starts to buffet. Nowhere does it state that wing dips and deep wing stalls occur like it does in the sim. Also all the A-10 videos available on youtube including cockpit recordings (HUD recordings & GoPro cams) show that the real life counterpart truly enough is a lot more forgiving when above critical AoA than the sim. I can provide you these videos & the stall charts if you want.

 

Something else regarding stalling, is the stall warning tone at high speeds. In the sim when above mach 0.6 and increasing the AoA the plane buffets and wing-stalls long before the stall tones (yes both of them). There is a HUD video of such a run on youtube where the pilot pulls the plane with the appropriate stall tones and even more AoA (visible by comparing the gun cross with the Flight Path Marker) than you can at the same speeds in DCS according to my testing, which I'm not saying are perfect but I tried this both in 1.5.x & 2.0x and I can't do the same AoA's as in the real life video without spiraling. This is detrimental to vertical high angle strafe runs (below -60° angle) where you have to pull the plane up at high speeds before hitting the ground in the sim. Just tell me if you want said video and I will share it.

 

 

Don't take this as criticism, I'm just really trying to help make this a better and more accurate plane for everyone :).

 

At 0.6 M the plane must stall at 22 units or 13 deg AoA and chopped tone is to be at 21. Try to pull up at 0.6 M and watch the gauge, please.

[SCU]

My mistake, I meant at speeds above 0.7 mach. Corrected

[Yo-Yo]

My mistake, I meant at speeds above 0.7 mach. Corrected

 

18 units stall and 17 - chopped tone

[mvsgas]

Love where this thread is going, very technical. Thanks guys.

I am still trying to understand the RL A-10, so I can compare to DCS and see what people are seeing. Like Sithspawn mention, I think first we all need to fully understand what the RL A-10 we are looking at. I only work on A-10 on passing, so I have little to no knowledge in the RL one and I always have problems understanding pilots books even after years of reading -1, -1-1, -1-2 etc. But I know military aircraft normally are continuously undergoing updates/upgrade (Called Time compliance technical orders or TCTO in the F-16 world) Some can and will affect performance, some are trivial.

 

Anyway, ITT is mention several times, my question to you guys;

- How do we know the engine is putting less thrust in DCS because of lower ITT?

In the RL aircraft, to me, it make little since why ITT is closely monitored since AFAIK, throttle positions affect that parameter apparently more directly, but in DCS the engine could and according to what I get from Yo-Yo post, produce the correct thrust. So are some of us saying they just want the ITT gauge to go higher or do we know by looking into the LUA that the engine are putting less lbs/kN of thrust?

- How much thrust are we talking about? Those few hundred degrees Celsius, do they represent hundreds of lbs of thrust or thousands?

 

Some mention speed, following some of the documentation mention (1A-10A-1-1)

I set a mission with a 0 drag index;

Baseline aircraft (drag index = 0) is clean with 11 pylons installed; leading edge slats

retracted; Pave Penny pylon and pod installed; and chaff/flare with cover plates installed.

We can't put cover plates in dispensers even when empty so I need to figure out how much drag we need to add plus, it mentions this;

On aircraft modified by T. O.

lA-10-1053, add drag index of O .038

to the aircraft drag.

Not sure if relevant.

 

At 2000 feet altitude and ambient temp of 11 Celsius and barometric pressure of 1088pa. no wind. Fuel was at 37%.

 

Now, what figure in the 1A-10A-1-1 are you guys using to determine speed? I was able to achieve 346 IAS but not sure what figure number in the T.O. to look at and compare.

 

Another thing I found interesting is that;

For configurations consisting of external

stores that result in a weight asymmetry,

an additional drag index must be determined

for the additional drag due to the deflection

of the ailerons required for trim. Figure

Al-2 presents a chart from which this

additional drag index may be determined for

any given flight condition

A-10 drag index is even affected by trim! :D

[David OC]

I will post this here as it relates, I see this comes up all over the forum

especially in the WW2 section on aircraft performance.

 

My question is,

What is a fair variation on performance from the same engine?

In WW2 how was the quality control when many companies where

tooling up to build the engines for quicker production.

 

They couldn't be all blue printed and tested, I bet some of the pilots

back then and even now on new jets jump in one and think, what the! This feels

quite a bit quicker/slower. I've seen this in car engines tested on dyno tuning machine with

stock standard manufactured cars.

 

So could you have a 5% performance variation in manufactured aircraft engines?

I know aviation tolerances are tighter than other engineering, but the Hitech Machinery I

work with have a mind of there own and are not always the same as they are on paper

once assembled.

 

If you even put a top class car like a Lamborghini on a dyno tune you will see different results between two of the same model cars.

Another example, Why can this CPU overclock way way more and be stable then the exact same CPU chip? Bad manufacturing or just (S Happens)

Edited August 4, 2016 by David OC

[mvsgas]

Talking about RL aircraft? In general, absolutely. In my limited experience, every aircraft and every engine is different. Not only from manufacturing but in general every day maintenance. That is why many aircraft parameters only tell you "regions". Example, core speed should not exceed "X" at "Y" throttle setting.

Here is a graph for the Greek F-16 with 129 GE engines circa 2003, see how many parameters are line through since there is not set limits/numbers

[ATTACH]145766[/ATTACH]

[David OC]

Talking about RL aircraft? In general, absolutely. In my limited experience, every aircraft and every engine is different. Not only from manufacturing but in general every day maintenance. That is why many aircraft parameters only tell you "regions". Example, core speed should not exceed "X" at "Y" throttle setting.

Here is a graph for the Greek F-16 with 129 GE engines circa 2003, see how many parameters are line through since there is not set limits/numbers

[ATTACH]145766[/ATTACH]

 

OK then, just to keep this friendly and for a bit of a laugh.

Does this mean we may have the lemon of the FM :(:smilewink:

 

I'm total OK with it if this engine is a complete possibility...?

How many years roughly before the A10 Engines need a rebuild?

It's been out since 2011:P

 

I like this debate and in no way am I trying to derail it.

It just seems to me everyone wants the top end performance on paper for all the aircraft here which is

not what you get IRL. ED shouldn't have to model the absolute best performance should they?

As long as it's with in specification and possible in RL then I'd be OK with it for any aircraft.

 

Note to ED put in +/- 5% variation on performance when you launch sim so I can watch everyone constantly restarting there multiplayer session.

Edited August 4, 2016 by David OC

[Enduro14]

It's great their is feedback. YoYo I ask kindly that you take a look at the document that was just recently provided of actual engine Tems data. If it needs a FM adjustment Rgr that if it does not Rgr that. It's obviously on another forum which I'm sure everybody knows all about.

 

Thank you for your time.

[Raistlen007]

 

Some mention speed, following some of the documentation mention (1A-10A-1-1)

I set a mission with a 0 drag index;

 

We can't put cover plates in dispensers even when empty so I need to figure out how much drag we need to add plus, it mentions this;

 

Not sure if relevant.

 

At 2000 feet altitude and ambient temp of 11 Celsius and barometric pressure of 1088pa. no wind. Fuel was at 37%.

 

Now, what figure in the 1A-10A-1-1 are you guys using to determine speed? I was able to achieve 346 IAS but not sure what figure number in the T.O. to look at and compare.

 

 

 

The A-10A chart I'm looking at is is a four way guide titled "Level Flight Maximum Speed Maximum Thrust" located at 1A-10A-1-1 A6-8 Figure A6-1 where you start from gross weight, move right to the altitude, go down the line to the drag index, and from there left to a final deviation from something called "Standard day" temperature, which gives you the final expected airspeed.

 

So all I'm missing from your description is the airplane's gross weight in thousands of pounds.

[Aginor]

Not sure if that got lost in the thread (some great posts here btw, thanks guys), so just to make sure I don't test something weird here are two questions for Yo-Yo:

 

1. Should we test in 1.5.4 or 2.0.3 or is the difference meaningless?

2. Are there any known differences between DCSWs atmosphere model and reality that could spoil our test results or should we just assume that atmospheric parameters from real life can be used for everything? I am asking because it can tell us what tolerances to set for our testing.

[NineLine]

It's great their is feedback. YoYo I ask kindly that you take a look at the document that was just recently provided of actual engine Tems data. If it needs a FM adjustment Rgr that if it does not Rgr that. It's obviously on another forum which I'm sure everybody knows all about.

 

Thank you for your time.

 

This is the document here (nobody is trying to hide anything, it was originally posted in a thread that was removed as it was opened in order to bypass a locked thread). The information that Yo-Yo shared with me (which is what the engines were modelled with I believe) shows the information he had is within range of the numbers on this document. The confusion I see right now is it was reported DCS only reaches 750 (posted earlier in this thread), but someone posted a pic showing it higher than that (again posted earlier in this thread). Again, I need to sit down and check it out as well, I hope this weekend.

 

[Vitormouraa]

Does the chart above say the IIT must reach 820/821? If you could explain this chart would be nice.

[AOG]

After reading through this thread I think I know what's going on. If my theory is correct the a-10 is experiencing a real world condition that's not uncommon for aircraft of that erra. I don't have access to the manual in question but most performance tables are based on standard day operations with reference fuels. That is fuel at the center of it density and energy band. And that's the problem. I think you will find those charts were based on JP4 or JP5. Aircraft today operate primarily on jet A or JP8. JP4 has a higher volatile content and is closer to car gas in content. Jet A is closer to karosene in consistency. This is important because jet A has a lower energy density than jp4. If you run Jet A in a fuel control rigged for JP4 the engine runs cooler and produces less power. I think that's what's happening here. ED is most likely simulateing JP8 or jet A in their engine model hence the performance difference. In the Real world most fuel controls of that erra had adjustments on the HMUs to compensate for the differences in the fuel types but they are a pain to adjust and rarely used. If anyone is interested in th details the American Petroleum Institute has a document that is pretty much the bible on aviation fuel. I think it's called the handbook of aviation fuels or something like that. You can find it online.

 

AOG

[Dojo]

Respectfully, I believe it's unfair to ask Sith to explain the data. Also, I can save you sometime and tell you right now that Snoopy was in error, the sim has for quite some time achieved higher than 750 ITT. (btw, Snoopy knows this, I believe he may have been misremembering and citing numbers from some time ago. I honestly haven't spoken to him about this thread, so I'm not sure why he forgot). However, watching this is a bit frustrating, because I believe the spirit of this thread is trying to understand a) is there really an issue and b) even if there is, why should we care?

 

Even with that minor error, the issue isn't (and has never been) that the engine doesn't achieve higher than 750 ITT (that is a distraction, I'll explain why a bit later... just wanted to write this note quickly before the thread spins in the wrong direction... which I agree with Sith, I really want to prevent as well).

 

The issue is that the engine doesn't achieve rated ITT. I'm drafting a response to Sith's initial post which I thought was an excellent way to resume the conversation. Just bouncing back and forth between this subject and real work at the moment. Please give me some time and I'll respond later today.

 

Thank you Sith, for re-opening the thread. I'm going to respond to it in the spirit in which I believe you re-opened it.

 

More soon!

Edited August 4, 2016 by Dojo

[mvsgas]

The A-10A chart I'm looking at is is a four way guide titled "Level Flight Maximum Speed Maximum Thrust" located at 1A-10A-1-1 A6-8 Figure A6-1 where you start from gross weight, move right to the altitude, go down the line to the drag index, and from there left to a final deviation from something called "Standard day" temperature, which gives you the final expected airspeed.

 

So all I'm missing from your description is the airplane's gross weight in thousands of pounds.

 

In DCS the weight was 29070 with a drag index of .78, so does this look about right? Since we can not have a drag index of zero in DCS, I added the drag from the note in page A1-2 (.38 ) plus the drag from page A1-10, Flare (chaff) all cartridges fired (.40).

[ATTACH]145784[/ATTACH]

Edited August 4, 2016 by mvsgas

[Enduro14]

This is the document here (nobody is trying to hide anything, it was originally posted in a thread that was removed as it was opened in order to bypass a locked thread). The information that Yo-Yo shared with me (which is what the engines were modelled with I believe) shows the information he had is within range of the numbers on this document. The confusion I see right now is it was reported DCS only reaches 750 (posted earlier in this thread), but someone posted a pic showing it higher than that (again posted earlier in this thread). Again, I need to sit down and check it out as well, I hope this weekend.

 

 

No worries I actually didn't see this thread until after everything happened. Will say I'm learning more about this aircraft from this thread and look forward to Dojo's post.

[Yo-Yo]

This is the document here (nobody is trying to hide anything, it was originally posted in a thread that was removed as it was opened in order to bypass a locked thread). The information that Yo-Yo shared with me (which is what the engines were modelled with I believe) shows the information he had is within range of the numbers on this document. The confusion I see right now is it was reported DCS only reaches 750 (posted earlier in this thread), but someone posted a pic showing it higher than that (again posted earlier in this thread). Again, I need to sit down and check it out as well, I hope this weekend.

 

 

 

 

As far as I can see, this is a record for a certain plane. The fact is that if the engine is worn within allowed limits, the gas temeparture raises as the necessary power or thrust is maintained by automatic governor.

 

That's why the ITT limits can be trimmed to maintain predicted Nf to have specified maximal thrust. This procedure is described in the engine manual - how to readjust T5 limiter.

 

As you can see in this doc, engines are a bit different, for example:

#1 has higher PLA setting but it achieves Nf predicted with higher ITT than #2

 

The current version of TF34 in DCS achieves 94%/83% Ng/Nf at 812C ITT that corresponds with GE data for -2 and -100. This ITT , as I wrote before, is for fresh mint engine.

[Raistlen007]

In DCS the weight was 29070 with a drag index of .78, so does this look about right? Since we can not have a drag index of zero in DCS, I added the drag from the note in page A1-2 (.38 ) plus the drag from page A1-10, Flare (chaff) all cartridges fired (.40).

[ATTACH]145784[/ATTACH]

 

I think it looks right, but I think we should standardize the scenario so we can replicate the results across different variables to rule out external factors.

[Aginor]

I think it looks right, but I think we should standardize the scenario so we can replicate the results across different variables to rule out external factors.

 

Agree. We can't test properly if the environment is a factor (which was also the reason for my last questions, see this post):

http://forums.eagle.ru/showpost.php?p=2864874&postcount=70